1. Field of the Invention
The present invention relates to an exhaust muffler for a vehicle, such as a motorcycle.
2. Description of the Related Art
A prior art exhaust muffler for a motorcycle, disclosed in Japanese Utility Model Registration No. 2513707 has a perforated inner pipe, an outer pipe, a glass wool mat, as a sound-absorbing element, packed in an annular space between the perforated inner and the outer pipe, and a steel wool mat interposed between the glass wool mat and the inner pipe to protect the glass wool mat from the damaging effect of the high-temperature, high-pressure exhaust gas.
A steel wool mat is formed by subjecting superposed bundles of ferrous metal filaments to needle punching to make the ferrous metal filaments entangled. A steel wool mat is wound around the perforated inner pipe to protect the glass wool mat wound around the steel wool mat from the damaging effect of the high-temperature, high-pressure exhaust gas.
The combustion efficiency and output of automotive internal combustion engines have been progressively increased in recent years, raising the temperature and pressure of the exhaust gas in the muffler. Consequently, ferrous metal filaments forming the steel wool mat for protecting the glass wool mat exert detrimental effects on the glass wool mat under a high-temperature, high-pressure condition, adversely affecting the durability of the glass wool mat.
The present invention has been made in view of the foregoing problem and it is therefore an object of the present invention to provide an exhaust muffler provided with a glass wool mat effectively protected from the damaging effect of the high-temperature, high-pressure exhaust gas on the glass wool mat.